1. Field of the Invention
The present invention relates to a non-destructive measurement apparatus for evaluating characteristics of a composite. More particularly, the present invention relates to a non-destructive measurement apparatus that may measure characteristics of a composite sample, such as thermal conductivity, electrical conductivity, and magnetic inductivity.
2. Description of the Related Art
Various thermal conductivity measurement methods for quantifying thermal conduction phenomenon of a composite sample have recently been suggested for use as standardized measurement methods. However, thermal conductivity values that are determined by using these various thermal conductivity measurement methods may vary significantly according to the specific measurement method used and/or the types of samples analyzed.
Due to the lack of a standardized system for visualizing thermal conduction phenomenon of an actual sample, visualization of the thermal conduction phenomenon is conventionally analyzed by the examining the effect of various variables, such as a peripheral environment, temperature, convection, humidity, an interfacial resistance between a sample and a heat source plate, the size of a sample, and a non-uniform heat transfer phenomenon from the heat source plate to the sample. Thus, conventional techniques limit the ability to analyze the thermal conduction phenomenon of a composite sample.
Standard experiments for thermal conductivity measurements include measuring thermal conductivity values of the composite sample and quantitative analysis of the resulting data. As noted above, different thermal conductivity measurement methods may provide different values for the same sample. In particular, in the case of a composite sample, thermal conductivity values may vary depending on whether the measurement was taken in a thickness direction, a lengthwise direction, or planar direction as a result of the orientation of a filler, the degree of dispersion, etc.
Most thermal conductivity measurement methods are optimized to measure thermal conductivity in the thickness direction of a sample. Thermal conductivity values in a lengthwise direction of the sample are very different according to the shape of a sample holder for testing in the lengthwise direction (or planar direction) or a method of manufacturing the sample and thus, the reliability of thermal conductivity measurement in the lengthwise direction of the sample is low.
In general, thermal conductivity of the composite sample occurs in an environment where temperature gradient exists. Thermal energy at a high temperature is transferred in the form of phonon via a crystalline lattice of the sample, and when a thermal image camera is used, thermal diffusion phenomenon of the sample may be detected as a variation in section (pixel) temperature and displayed on a display with color contrast.
However, as described above, there is no standardized system for visualizing thermal conduction phenomenon in an actual sample. Thus, there is a limitation in analyzing visualization of the thermal conduction phenomenon due to the effect of various variables, such as the effect of peripheral environment, such as temperature, convection, and humidity, an interfacial resistance between a sample and a heat source plate, the size of a sample, and a non-uniform heat transfer phenomenon from the heat source plate to the sample.
In particular, in the case of a polymer composite sample, the orientation of a filler and the degree of dispersion may vary according to a method of manufacturing the polymer composite sample. In general, in case of a sample manufactured by injection, a filler is oriented in a direction of injection, i.e., a lengthwise direction of the sample by receiving a transfer force so that the filler forms a heat transfer path in the direction of injection, and therefore the thermal conduction characteristics in the direction of injection are higher than in the thickness direction of the sample.
Thermal conduction characteristics may vary according to a number of variables such as, for example, the injection condition, crystallinity of the polymer resin, the size and shape of a filler, and/or surface characteristics of the filler. Thus, there is a need for clear analysis of thermal conduction characteristics in the lengthwise direction and the thickness direction of the sample.
Destructive measurement is generally used to analyze various characteristics of a composite. In destructive measurement, the sample is destroyed so as to check a combination state of the sample or a disconnection state of a filler or fiber. In destructive measurement, the sample is destroyed so that re-measurement or partial characteristic re-analysis is not possible. Thus, in order to overcome the limitation, non-destructive measurement should be performed.
Non-destructive measurement generally includes measurement using X-rays and neutrons. Unfortunately, the cost for non-destructive measurement is high, and it takes a long time to perform non-destructive measurement. Thus, non-destructive measurement cannot be repeatedly performed in a cost-effective manner.
In addition, electrical conductivity of a composite sample according to the conventional art is measured using an electrically connected sensor that is grounded by a user at a desired position. Unfortunately, this lowers the reliability of measurement to the requirement for manual positioning of the sensor, and if the size of the composite sample and/or the number of positions of the sample to be measured is increased, the time and manpower required for measurement is very large. Accordingly, there is a need for an apparatus for non-destructively measuring various material characteristics, such as thermal conductivity, electrical conductivity, and magnetic inductivity.